EFFECTS OF DDT SPRAY ON STREAM BOTTOM ORGANISMS 

 IN TWO MOUNTAIN STREAMS IN GEORGIA 



By 



Paul J . Frey 



Bureau of Sport Fisheries and Wildlife 



Fish -Pesticide Research Laboratory 



Gulf Breeze, Florida 



ABSTRACT 



DDT was sprayed at 0.5 pound per acre for elm spanworm 

 control in two drainages in north Georgia in both 1959 and 

 1960. In one drainage, precautions were taken to avoid the 

 stream, and no significant mortality to aquatic organisms 

 resulted. In the other drainage, DDT reached the stream 

 in a normal spray operation, and serious depletion of aquat- 

 ic invertebrates resulted. Recovery of bottom organisms 

 was rapid, and total numbers of invertebrates were up to 

 pre -treatment levels after four months. 



CONASAUGA LAKE AREA 



The elm spanworm, Ennomus sub - 

 signarius (Hbn.), became established in the 

 Chattahoochee National Forest in the early 

 1950's. In the late 1950's the infestation spread 

 from high isolated points to lower levels and in 

 a general northeasterly direction. Protection 

 of the forest in two important recreational areas 

 necessitated the use of control measures by the 

 Forest Service in 1959 and 1960. The two heavi- 

 ly infested areas were treated by helicopter 

 with one -half pound of DDT per gallon of oil per 

 acre. This paper reports a study by the Bureau 

 of Sport Fisheries and Wildlife on the effects of 

 these treatments on the stream-bottom organ- 

 isms in two small streams. 



DESCRIPTION OF THE STUDY STREAMS 



The two study streams (fig. 1), one in 

 the Conasauga Lake area near Chatsworth, Geor- 

 gia, and the other originating on Brasstown Bald 

 near Blairsville, Georgia, are typical of high 

 mountain streams in this region. The treated 

 section of the Conasauga Lake stream is one- 

 half mile long and falls approximately 200 feet 

 enroute. The stream originates from small 

 springs which have a flow of approximately 50 

 gpm. From this point the volume increases 

 rapidly and reaches a volume of approximately 



Figure 1.-- Diagrammatic drawing of control 

 and experimental streams showing positions of 

 sampling stations, and the relationships between 

 experimental and control streams . 



